The association between thyroid cancer and insulin resistance, metabolic syndrome and its components: A systematic review and meta-analysis

Background: Thyroid cancer is rapidly increasing in incidence worldwide in the past several decades, same as the incidence of metabolic syndrome. We performed a system review and meta-analysis of the association between metabolic syndrome, its components and insulin resistance and thyroid cancer incidence. Methods: We searched several computer-assisted databases PUBMED, EMBASE and ISI Web of Science to identify studies published before 31st January 2018. Every study must report either risk estimates of thyroid cancer incidence with 95% confidence interval (CI) or related data can speculate. Two investigators independently identified eligible studies and extracted data. Evaluating the summaries of relative risk estimates use both fixed and random effects methods. Results: We found 42 articles met the inclusion criteria of this review. There is an increased risk for thyroid cancer for patients with insulin resistance (relative risk [RR] = 1.59, 95% confidence interval [CI] = 1.12-2.27, P = 0.01), dysglycemia (RR = 1.40, 95%CI = 1.15-1.70, P < 0.001), high BMI (RR = 1.35,95%CI = 1.23-1.48, P < 0.001) and hypertension(RR = 1.34,95%CI = 1.22-1.47, p < 0.001). However, patients with dyslipidemia, both total cholesterol (RR = 1.09, 95%CI = 0.98-1.21, P = 0.13) and triglyceride (RR = 1.01, 95%CI = 0.91-1.12, P = 0.82) was not associated with thyroid cancer. Conclusions: Our meta-analysis showed Insulin Resistance, dysglycemia, high BMI and hypertension significantly increased the thyroid cancer risk. These results may help identify people with high risk of thyroid cancer and change to healthy life style.